In the reforming of metal sheets arranged in a vertically extending stack it is common to remove the uppermost sheet from the stack and transfer it from the stack to another position where the sheet may undergo reforming procedures. If the confronting surfaces of the stacked sheets are smooth or have a film of lubricant thereon it sometimes is difficult to separate the upper-most sheet from the stack. This problem can be overcome by providing a magnetic field adjacent the upper end of the stack of sheets so as to provide a gap between the upper sheets, thereby facilitating the separation of the uppermost sheet from the remainder of the stack. Apparatus for accomplishing this objective is illustrated in a number of prior patents, of which U.S. Pat. No. 5,651,541 is illustrative and the disclosure of which is incorporated herein by reference.
It is preferred to use permanent magnets, rather than electromagnets, for the creation of the magnetic field because permanent magnets are less expensive and require less maintenance. In those instances in which the permanent magnets are very powerful, however, it sometimes is difficult to effect movement of the magnets in a direction away from the stacked sheets because the magnetic attraction is so great. Because of the power of the magnets the force which must be applied to move the magnets in a direction away from the stack of sheets may be greater than that which can be provided without risking damage to the fanner construction, or to the edges of stacked sheets, or both.
It is the object of this invention, therefore, to provide apparatus which can generate adequate force to effect controlled movements of very powerful magnets and in such manner as to minimize the possibility of damage resulting from such movements.